1. Technical Field
The invention generally relates to a dispenser for a flowable substance and, in particular, the invention relates to a one piece fluid dispenser having two chambers separated by a membrane.
2. Background of the Invention
Different types of containers and dispensers for the distribution of material are known within the packaging industry. One example is described in U.S. Pat. No. 3,759,259 issued Sep. 18, 1973 to Andrew Truhan. The Truhan patent discloses a combination applicator and container for medicinal substances. The applicator includes a holder and a fibrous wadding of cotton. The container has flexible walls and a flat seal that spans the container opening. The flat seal is heat sealed to the interior surface of the container. The flat seal is perpendicular to the flexible walls and ruptures upon the application of inward force to the container side walls. In another embodiment, the flat seal includes one or more score lines which form lines of weakness or burst lines when an inward force F is applied to the container side walls.
U.S. Pat. No. 3,684,136 to Baumann discloses a receptacle for receiving and mixing liquid and/or solid substances. The receptacle includes a lower mixing chamber M, an upper secondary chamber S, and a foil dividing wall. The lower surface of dividing wall is convex and the top surface of the wall is concave. In the first embodiment, the surface of the dividing wall features a scored notch(es), that signifies a weakened portion of the dividing wall. The notches can be arranged in a star or cross orientation. To tear the dividing wall, lateral pressure P is applied to receptacle walls adjacent to the dividing wall. When lateral pressure P is terminated, the dividing wall returns to its original shape and the opening will close. In the second embodiment, the receptacle includes outer projections which indicate the direction in which the notches should be disposed during assembly.
In both Truhan and Baumann, the seal separating the chambers has score lines which are formed from the removal of material from the seal itself. The removal of material is necessary to sufficiently weaken the seal structure to facilitate rupture. However, the removal of material compromises the burst strength of the seal and can lead to inconsistent and untimely seal rupture. As a result, the effectiveness of both the seal and the device is reduced.
Furthermore, with both devices it is necessary to under fill the container with liquid leaving ample air space. This under filling increases the chance of accidental seal rupture from pressure on the container. Consequently, the volume of liquid stored within the chamber must be reduced.
Lastly, the dispensers disclosed in Truhan and Baumann are designed to release the entire fluid contents at one time. Thus, the user cannot control the distribution and application of the liquid over a period of time.
The present invention is provided to solve these and other problems.
The present invention provides a dispenser for discharging either a liquid or solid material. To this end, there is a device provided having two adjacent chambers separated from each other by a novel rupturable web or fracturable membrane. The first chamber has a distal end and is a storage chamber for the material. The second chamber has a proximate end and receives the material when released from the first chamber by rupture of the membrane. The first and second chambers are defined by a peripheral wall with an elongated axis forming a sleeve or cylinder. After the material is added to the first chamber, the distal end, the end opposite from the membrane, is sealed to hold the material in the first chamber. The first chamber can be closed off or sealed by pressing the sides of the end of the chamber together and heat sealing or applying an adhesive. Alternatively, the first chamber can be sealed by applying a cap over the end of the tube. The membrane separating the chambers is provided with a weld seam and is broken by lateral force on the membrane to allow the fluid to flow from the first chamber into the second chamber. The thickness of the membrane can be varied, thereby either increasing or decreasing the amount of applied force needed to rupture the membrane.
In accordance with the invention, the web is preferably disk-shaped having a series of radial disposed uniform depressions on one surface of the disk and extending from a center point of the disk in the form, for example, of spokes on a wheel. The thickness of the disk is lesser at the depressions. When the disk is compressed by exerting pressure on the edge of the disk, the web breaks along the depressions forming a series of finger-like triangular projections extending from the face of the disk. Since the fingers are widest where they contact the container wall, the center section of the disk preferably opens first to material flow. The amount of material that can pass into the second chamber is controlled by the degree of opening which corresponds to the depressed areas and the pressure applied to the chamber. In a preferred embodiment, the depressed areas are formed on only one side of the disk but could also have depressed areas on both sides of the disk. The fingers formed as a result of the compression will extend in the direction of the flow of the material. This arrangement permits an even flow of the material.
According to another aspect of the invention, the novel membrane has opposing first and second surfaces and contains a weld seam. The membrane is formed by a first segment of injected molded material that abuts a second segment of injected molded material to form the weld seam. The segments abut at an interface area. The membrane thickness is reduced at the weld seams. In one preferred embodiment, the weld seam comprises a plurality of weld seams that are generally pie-shaped and are molded at right angles to the interior surface of the dispenser. The mold segments are widest at their base where they extend from the interior dispenser surface and narrow as they radially extend toward a center portion of the membrane.
Under normal use and operation, the membrane partitioning the first and second chambers can only be ruptured by the precise administration of force on the membrane. The membrane will not rupture when the first chamber is compressed by normal hand pressure. Conversely, extreme force loads are required to rupture the membrane by compressing the first chamber. Such forces would not be present during normal use and handling of the dispenser.
When the membrane is compressed by exerting pressure on the edge of the membrane, the membrane ruptures only along the weld seams. Unlike prior art devices, the membrane rupture is predictable and controlled at the weld seams. The amount of material which can pass into the second chamber is controlled by the degree of membrane opening which is directly controlled by the amount of force applied to the membrane by the user.
According to another aspect of the invention, the outer surface of the chamber walls can be provided with a marking to indicate the preferred location where force should be applied to rupture the membrane. In one preferred embodiment, the marking is an external extension. Such an extension can be in the form of a thumb pad, which corresponds to the location where force should be applied. Alternately, the outer surface of the chamber can have any type of raised area or projection such as a circular band around the outside of the chamber to indicate the desired point of force application. The outer surface could also have an indicia or other marking to indicate where force should preferably be applied.
In accordance with the invention the dispenser is produced in a unitary configuration by a molding process. The mold has a cavity formed to correspond to the outer surface of the chambers. Two laterally opposed pistons, or core pins, are extended into the mold cavity to form the inner surface of the chambers. An end of one of the pistons is configured with a raised structure that facilitates the formation of weld seams, or depressions on the membrane. The membrane structure can be in many configurations, including but not limited to a cross or star.
The molding process is initiated by the injection of thermoplastic material into the cavity. Once injection is complete, the mold is then cooled by circulating a cooling medium, such as water, in a cavity surrounding the mold. The core pins are then retracted to allow release of the molded product.
The flowable material to be utilized can be fed into the first chamber and the end of the chamber sealed. Because the release of the material depends on the application of pressure to the web to break the weld lines, and not the pressure of the material fluid against the web, it allows the chamber to be filled with small quantities of material. If the seal is to be broken by the pressure of liquid material as in the prior art devices, sufficient liquid has to be present to create the required hydraulic pressure when compressed. Further, the dispenser of the invention allows the dispensing of non-liquids such as a powder which would not exert any hydraulic pressure.